Sulfidization is used in conditioning a flotation pulp and comprises addition of soluble, and usually alkaline, sulfides to an aqueous pulp, such as a leach pulp, to produce a sulfide-metal layer on an oxidized ore surface. The ore can then be floated as if it were a sulfide ore. While highly successful in the processing of some ores, such as lead ores, sulfidization has been of limited utility in connection with copper ores.
Copper pulps contain signigicant amounts of pyrites and complete copper sulfidization results in excessive activation of these pyrites. While such activation does not adversely affect the rougher flotation of the copper, it does make pyrite rejection in the subsequent cleaner flotation extremely difficult. This is due to the fact that the activation of the pyrites results in deposition of elemental sulfur at the pyrite surface and this sulfur layer results in a naturally hydrophobic surface that is resistant to normal pyrite depression techniques during cleaner flotation. Attempts to overcome this problem by severe pyrite depression environments have not been successful since they result in very poor copper recovery in the cleaner flotation circuit.
In efforts to overcome such unsatisfactory flotation and copper loss, incomplete sulfidization of the copper has been tried. However, this is equally unsuitable since insufficient sulfidization results in inadequate sulfide conditioning of the copper thereby preventing optimum rougher flotation recovery and consequent copper loss.
Thus, with copper pulps it has not been possible heretofore to optimize copper flotation recovery while minimizing pyrite activation and copper loss when sulfidization is used.